The invention relates to an absorbing wound dressing for covering and cleaning a strongly wetting, infected wound, as well as effected areas in skin and tissue diseases, as well as a method for making that dressing.
It is known that a modern wound dressing can be used in defective wounds of different genesis, particularly in problem indications, like Ulcus cruris, dekubitalulzera, diabetic gangrene, chronically infected wounds and burn wounds of 2nd and 3rd degree, whereby the wound dressing can be made toxically unobjectionable, without problems, able to be stored and it must be sterilizeable; furthermore, it must have a sufficient gas permeability for ventilation of the wound, it must adhere very well to the wound area without bonding itself to the scab of the wound, it must be characterized by a high degree of absorbability for wound healing features (wound exsudate, bacteria, necrotic cell material) and must be intensively wound cleaning and thereby infection reducing, and in addition it must be granulation and/or epithelisation effective.
It is also known that the conventional wound dressings which mainly consist of fabric or a texture made of natural or synthetic fibers, but above all, from regenerated cellulose in form of short or long fibers, do not meet completely the aforementioned criteria; in particular, they bond themselves to the wound or the scab of the wound, so that during the changing of the wound dressing the protective wound scab is torn open, the wound becomes irritated and the healing process is interrupted and naturally prolonged; furthermore its absorbability is limited, whereby in particular bacteria is not absorbed, so that consequently a reduction of the infection is very often only possible with added antibacterial substances, like antibiotics or sulfonamide.
To overcome these disadvantages, would dressings were developed (for example DD-PS 97547, DE-OS 1209702, DE-OS 1,254,295, DE-OS 1492409, DE-OS 1629425, U.S. Pat. No. 2,923,298, U.S. Pat. No. 3,012,918, U.S. Pat. No. 3,043,301, U.S. Pat. No. 3,285,245, U.S. Pat. No. 3,434,472, U.S. Pat. No. 3,438,371. U.S. Pat. No. 3,441,021, U.S. Pat. No. 3,446,208, U.S. Pat. No. 3,457,919, U.S. Pat. No. 3,579,628, U.S. Pat. No. 3,750,666) which on the wound side are provided with a non-adhering, flexible perforated plastic foil made of polyethylene, polypropylene, polyvinylchloride, polyvinylacetate, polyethylene terephthalate, ethylene/vinylacetate-copolymers, polyacrylates or polyvinylpyrrolidon; wound dressings are also known which are provided on the wound side, instead of the perforated plastic foil, equally effective thin perforated metal foils made from silver, aluminum or zinc (for example, DE-OS 1161384, DE-OS 1417379, U.S. Pat. No. 3,934,066). Such wound dressings do not bond themselves to the wound, they also permit the wound exsudate to permeate through the perforations so that it can be absorbed by the provided absorbing layers (cellulose, molded cotton, cotton felt). Apart from this fact that the absorbability of such wound dressings is not basically increased, the smearing-purulent exsudatees of strongly infected wounds can also block the openings, thus creating exsudate products which offer excellent growth capabilities for bacteria; one additional disadvantage, which cannot be completely excluded, is the friction effect of such wound dressings which are provided with metal layers.
An increased absorbability of the wound dressings is obtained by using such natural or synthetic materials which are water insoluble, on the one hand, but swell with water. Such materials are, for example, Chitin and Chitosan (MIT Sea Grant Rep. MIT SG 1978, Proc. Int. Conf. Chitin/Chitosan 1977, pages 296-305), collagen (DD-PS 56587, GB-PS 1195062, U.S. Pat. No. 3471598, U.S. Pat. No. 3,491,760, U.S. Pat. No. 3,800,792, U.S. Pat. No. 4,089,333), wet cross linked cellulose fibers, particularly formalized cotton and synthetic silk fibers (DE-OS 1492365), which advantageously contain 5-20 mass-% of the Na-salt of the carboxymethyl cellulose (CMC) (DE-OS 2638654), mixed fibers from regenerated cellulose and Na-CMC (U.S. Pat. No. 3,858,585) or cross linked CMC-products (DE-OS 2357079), hydrolyse products of cross linked copolymer from vinyl ester and unsaturated carbonic acids (DE-OS 2653135), cross-linked polyacrylamide and sulfonized polystyrole (DE-OS 1617998, DE-OS 1642072, U.S. Pat. No. 3,669,193), cross linked poly-N-vinylpyrrolidone and morpholinone (U.S. Pat. No. 3,810,468), cross linked dextrane, starches and starch derivatives (DD-PS 109513, DE-OS 2403269), as well as foam materials made from urea/formaldehyde or melamin/formaldehyde resins (DE-OS 1246173, DE-OS 1247553), which additionally may contain butadien/styrol or butadien/acrylnitrile-copolymer, (U.S. Pat. No. 3,314,425) and such from polyurethane (DE-OS 2103590, GB-PS 1065994, GB-PS 1253845, U.S. Pat. No. 3,157,178, U.S. Pat. No. 3,648,692, U.S. Pat. No. 3,975,567, U.S. Pat. No. 3,978,855). The hydrolyse products of the cross linked vinylacetate/methacrylate-copolymer can absorb, for example, 100 times of its own weight of water or wound exsudate, the cross linked polyacrylamide up to 70 times and the cross linked poly-y-vinylpyrrolidone at least 15 times.
Most of the wound dressings are fabrics or texture materials of fiber-like articles, i.e., they are being used in form of premade flat shaped articles. The covering of the wounds with particulate matter, like powders or the like, is performed comparatively seldom, although they have great advantages over flat shaped wound dressings, in particular with uneven or fissued wounds.
Useable particulate materials for wound coverings are described in DE-OS 2403260, for example. These are micro pearls of cross linked polysaccharide and polysaccharide derivatives, in particular cross linked dextrane which are applied directly on the wound. It is further known, that for the same purpose spherical regenerated cellulose particles can be used. Both materials have a high degree of absorbability for wound secretions and are able to remove bacteria, fungi, toxins, inflammation mediators (prostaglandine) and plasma proteins (fibrinogen-fission products).
Despite of many proven positive advantages, the two particulate materials have still some disadvantages which limit a wide use thereof. The particles which are build up from cross linked dextranes, whose gel matrix has genuine pores, neither in the dry state, nor in the wet state, do swell during contact with water or watery solutions with a strong volume enlargement and result in a gel layer which reduces the gas permeability therein. This disadvantage is overcome with the regenerated cellulose particles which have a macroporous structure and therefore absorb water without swelling, but their porosity causes to absorb non-watery medium, for example, organic solvents, which can have unfavorable effects at different types of applications; their sterilization with .gamma. rays is combined with a yellow to brownish discoloration. The aforementioned particulate materials can be made in accordance with known methods, for example, by acidifying the cellulose particles with emulsified cellulose solvents (SE-PS 382066, U.S. Pat. No. 3,597,350), by instilling viscose solutions in suitable coagulation baths (JP-PS 73.21738, JP-PS 73.4082, JP-PS 73.60753), by a short time heating of particulate cellulose ester, like, for example, cellulose acetate in silicon oil to 290.degree.-300.degree. C. (JP-PS 78.07759, JP-PS 78.86749), or by thermic coagulation of vixcose dispersions (CS-US 172640, DD-PS 118887, DE-OS 2523839, U.S. Pat. No. 4,055,510). However, the cellulose particles which are obtained by this method result in an absorption capable wound dressing of the aforementioned quality if they are so dried that their macroporosity is preserved. In accordance with the present state of the art, this can only be achieved with special drying methods which are expensive and economically unfavorable.